My Name is Anoop kumar I am Student of Central University of Uttarakhand ( HNBGU ) This PPT is Habitat Management and Techniques 👍

1. HEMVATI NANDAN BAHUGUNA
GARHWAL UNIVERSITY
SRT CAMPUS BADSHAHITHAUL
DEPARTMENT OF ZOOLOGY
TOPIC: VITELLOGENESIS
PAPER: DEVELOPMENT BIOLOGY
SUBMITTED BY: ANOOP KUMAR
M.SC. ZOOLOGY 1ST SEM
ROLL NO. 25

2.  POINTS TO BE DISCUSSED:
• DEFINITION OF VITELLOGENESIS
• CHARACTERISTIC
• TYPES OF YOLK
• GRANULAR YOLK
• YOLK PLATELETS
• FUNCTION
• REFERENCE

3. DEFINITION OF VITELLOGENESIS
• From Latin Vitellus – yolk & Genero – produce
• Vitellogenesis (also know as yolk deposition) is the
process of yolk formation via nutrients being deposited in
the oocyte, or female germ cell involved in reproduction
of lecithotrophic organisms.
• In insects, it starts when the fat produces vitellogenin
protein.

4. CHARACTERISTIC
 Yolks is the most usual form of food storage in the egg.
 Yolks appear in the oocyte in the secondary period of their
growth celled vitellogenesis.
 Thus, the formation and deposition of yolks is known as
vitellogenesis.
 Yolks is a complex variable assembled component.
 The principle component are protein, phospholipid & fats in
different combination.
 Depending upon these component yolks is distinguished into
protein yolks & fatty acid
 For eg- the avain contain 48.19% water, 16.6% protein, 32.6%
phospholipids & fats , & 1% carbohydrates

5. TYPES OF YOLKS
 In animals, the yolk is of 3 types
 1.Granular yolk
 2. Yolk platelets
 3. Yolk sphere

6. 1. GRANULAR YOLK
• It is the characteristic feature of invertebrates & lower
chordates likes amphooxus & tunicates.
• The protein yolk is composed of fine granules which is evenly
distributed into the cytoplasm of oocyte .
2. YOLK PLATELETS
• It is found is most vertebrates like cyclostomes, lung fishes,
amphibians, reptiles,& birds.
• The yolk occur in the form of large granules known as yolk
platlets.
• The yolk platlets are oval & flattened in one plane.

7. THE YOLK PLATLETS CONTAIN 2 MAIN
PROTEINACEOUS
• 1 Phosphovitin - it is highly phosphorylated protein
• Its molecular weight is 35000 Dalton, 8.5% of phosphorus
content is present.
• 2. Lipovittelin – it is a protein major bound to lipid.
• Its molecular weight is 4000 D, 17.5% lipid content is present.
• In yolk platlets, 2 molecules of phosphovitin are associated
with one molecule of lipovittelin a structural unit.
• The units are being arranged in platelets in a crystalline
lattice with a regular hexagonal packing
• The yolk platelets of bony fish have fat droplets inside its
mass

8. • 3. YOLK SPHERE
The yolk of birds, reptile & bony fishes lies in a compact mass in
the interior of a egg.
The cytoplasm is restricted to their layar on the surface of the
egg

9. FUNCTION
• It store food in the egg
• It influence the differentiation of neoplasm
pattern of cleavage.
• The size of egg is determined by amount if yolk
present in it.
• Its responsible for morphogenetic movement of
elastomer during gastrulation
• The mature of development of an organism is
governed by amount of yolk present in the egg

10. REFERENCE
• DEVELOPMENT BIOLOGY (P.C JAIN); SEVENTH
EDITION: VISHAL PUBLICATION(2014)
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC790
1893/